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The information-entropy measures of the complexity of nets are proposed that take into consideration both the vertices and edges of nets. The parameters quantify the amount of Shannon information per element (vertex or edge) and per the translationally independent parts of the nets. The nets can be classified according to their complexity into very simple (0–20 bit per cell), simple (20–100 bit per cell), intermediate (100–500 bit per cell), complex (500–1000 bit per cell), and very complex (>1000 bit per cell). The information entropies for 1936 3D nets were calculated and analysed, showing that the simplest (information-poor) nets possess the lowest transitivities. The majority of the most common nets in metal–organic frameworks (MOFs) are the simplest nets within their respective categories (i.e. among the nets with the same coordination of vertices). Since the information is directly related to entropy, which is understood as a statistical parameter, the preference of the simplest nets in MOFs is at least in part governed by their low information contents and high configurational entropies. [ABSTRACT FROM AUTHOR]

Flexible crystal structures, which exhibit single-crystal-to-single-crystal (SCSC) transformations, are attracting attention in many applied aspects: magnetic switches, catalysis, ferroelectrics and sorption. Acid treatment for titanosilicate material AM-4 and natural compounds with the same structures led to SCSC transformation by loss Na+, Li+ and Zn2+ cations with large structural changes (20% of the unit-cell volume). The conservation of crystallinity through complex transformation is possible due to the formation of a strong hydrogen bonding system. The mechanism of transformation has been characterized using single-crystal X-ray diffraction analysis, powder diffraction, Rietvield refinement, Raman spectroscopy and electron microscopy. The low migration energy of cations in the considered materials is confirmed using bond-valence and density functional theory calculations, and the ion conductivity of the AM-4 family's materials has been experimentally verified. [ABSTRACT FROM AUTHOR]

The chemical and structural diversity of minerals containing sulfur as an essential mineral-forming element has been analyzed in terms of the concept of mineral systems and the information-based structural and chemical complexity parameters. The study employs data for 1118 sulfur mineral species approved by the International Mineralogical Association. All known sulfur minerals belong to nine mineral systems, with the number of essential components ranging from one to nine. The chemical and structural complexity of S minerals correlate with each other; that is, on average, chemical complexification results in structural complexification. The minerals with S–O bonds (sulfates and sulfites) are more complex than those without S–O bonds (sulfides and sulfosalts). However, the most complex sulfur mineral known so far is incomsartorite, Tl6Pb144As246S516, a sulfosalt. The complexity-generating mechanism in sulfides and sulfosalts is the complex combination of different modules excised from parent PbS or SnS archetypes with the subsequent formation of superstructures. The drivers for structural complexity in sulfates are more diverse and, in addition to modular construction and superstructures, also include a high hydration state, the presence of polyatomic clusters, and framework complexity. The most complex Martian minerals are most probably halotrichite-group minerals. The chemical and structural complexity increases with the passage of geological time with the formation of the most complex sulfosalts at Lengenbach (Swiss Alps) triggered by life (activity of sulfur-reducing bacteria). [ABSTRACT FROM AUTHOR]

Single crystals of Na2Cu+[Cu2+3O](AsO4)2Cl (1) and Cu3[Cu3O]2(PO4)4Cl2 (2) were prepared by chemical vapor transport reactions. Both crystal structures are based upon the same [O2Cu6]8+ chains formed by corner-sharing (OCu4)6+ tetrahedra and interconnected by (TO4)3− (T = P, As) tetrahedra into porous {[OCu3](TO4)2Cl}3− frameworks. The channels within the frameworks are occupied by Na+, Cu+ and Cl− ions in the crystal structure of 1, whereas the channels in the structure of 2 contain edge-sharing CuO4Cl tetragonal pyramids. Both compounds are structurally related to the previously described synthetic Na2Cu+[Cu2+3O](PO4)2Cl and NaCu2+[Cu2+3O](PO4)2Cl. The compound 2 is structurally and chemically related to yaroshevskite, Cu3[Cu3O]2(VO4)4Cl2, a mineral discovered in volcanic fumaroles, but the two structure types are drastically different. The crystal chemical analysis of the title and related compounds allows to recognize a family of at least four compounds based upon {[OCu3](TO4)2Cl}3− frameworks with channels occupied by different chemical constituents. [ABSTRACT FROM AUTHOR]

The complexities of chemical composition and crystal structure are fundamental characteristics of minerals that have high relevance to the understanding of their stability, occurrence and evolution. This review summarises recent developments in the field of mineral complexity and outlines possible directions for its future elaboration. The database of structural and chemical complexity parameters of minerals is updated by H-correction of structures with unknown H positions and the inclusion of new data. The revised average complexity values (arithmetic means) for all minerals are 3.54(2) bits/atom and 345(10) bits/cell (based upon 4443 structure reports). The distributions of atomic information amounts, chemIG and strIG, versus the number of mineral species fit the normal modes, whereas the distributions of total complexities, chemIG,total and strIG,total, along with numbers of atoms per formula and per unit cell are log normal. The three most complex mineral species known today are ewingite, morrisonite and ilmajokite, all either discovered or structurally characterised within the last five years. The most important complexity-generating mechanisms in minerals are: (1) the presence of isolated large clusters; (2) the presence of large clusters linked together to form three-dimensional frameworks; (3) formation of complex three-dimensional modular frameworks; (4) formation of complex modular layers; (5) high hydration state in salts with complex heteropolyhedral units; and (6) formation of ordered superstructures of relatively simple structure types. The relations between symmetry and complexity are considered. The analysis of temporal dynamics of mineralogical discoveries since 1875 with the step of 25 years show the increasing chemical and structural complexities of human knowledge of the mineral kingdom in the history of mineralogy. In the Earth's history, both diversity and complexity of minerals experience dramatic increases associated with the formation of Earth's continental crust, initiation of plate tectonics and the Great Oxidation event. [ABSTRACT FROM AUTHOR]

Perryite, natural Ni-silicide, is a minor but regular constituent of the metal phase in enstatite chondrite (aubrite) and enstatite chondrite meteorites. Its synthetic analog was shown to have promising catalytic properties. The first-time solution of the crystal structure of natural perryite was completed on the material from the Mount Egerton aubrite. The mineral is trigonal, R-3c, a = 6.6525(5), c = 37.998(5) Å, V = 1456.3(3) and Z = 6. The structure was refined to R1 = 0.0137 based on 457 independent observed reflections. The chemical formula obtained from the structure refinement, (Ni14.14Fe1.88)S16.02PSi5, agrees with that derived from the electron microprobe data, (Ni13.39Fe2.65Co0.01)S16.05P1.22Si4.74. This research showed that P and Si in perryite are ordered, resulting in the simplified formula (Ni,Fe)16PSi8, in contrast to the currently accepted variant (Ni,Fe)8(Si,P)3. The detailed results of EBSD study reveal previously unknown relationships between perryite, associated a-(Fe,Ni) metal (also known as kamacite) and schreibersite, (Fe,Ni)3P. Since enstatitic meteorites represent the early stages of nebular accretion, our results demonstrate that the crystal-chemical factor could affect the differentiation of chemical elements upon the onset of the Solar System formation. [ABSTRACT FROM AUTHOR]

The crystal structure of nikmelnikovite, Ca12Fe2+Fe3+3Al3(SiO4)6(OH)20, a new member of the garnet supergroup from Kovdor massif, Kola Peninsula, Russia (R $\bar{3}$ , a = 17.2072(6), c = 10.5689(4) Å, V = 2710.1(2) Å3 and Z = 3) has been refined to R1 = 0.046 on the basis of 1184 unique observed reflections. Nikmelnikovite is the first mineral species in the garnet supergroup that has a trigonal (rhombohedral) symmetry. The relationship between its unit cell and the pseudocubic (ideal garnet) unit cell can be described by the transformation matrix [1 $\bar{1}$ 0 | 01 $\bar{1}$ | ½½½]. The crystal-chemical relations between the ideal Ia $\bar{3}$ d garnet and the nikmelnikovite structure type can be described by the following series of imaginary modifications: (1) the symmetry is lowered according to the Ia $\bar{3}$ d → R $\bar{3}$ group–subgroup relationship; (2) the cation sites are split according to the following sequences: X → {X1, X2}; Y → {Y1, Y2, Y3, Y4}; Z → {Z1, Z2}; (3) the X sites remain fully occupied by Ca; (4) each Y site is occupied predominantly by a distinct chemical species: Y1 → Al (Al site), Y2 → Fe2+ (Fe1 site), Y3 → Fe3+ (Fe2 site), Y4 → vacancy (Mn site); (5) one of the Z sites (Z1) is occupied by Si, whereas the other site (Z2) is predominantly vacant. The crystal-chemical formula that takes into account the transition between the archetype and the nikmelnikovite structure type can be described as X{Ca12}Y[Fe2+Al4Fe3+2□]Z(Si6□6)O24(OH)20□4. The structural complexity of nikmelnikovite (4.529 bit/atom and 434.431 bit/cell, after H-correction) is higher than those for andradite, grossular and katoite, which is typical for low-temperature minerals formed after primary minerals with simpler structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • the review of structural diversity of antiperovskites includes more than 280 compounds. • the review covers a wide range of chemical compounds, including oxides, halogenides, nitrides, etc. • 45 topological types of antiperovskite units are considered and analysed. • the topological principles of antiperovskite constructions are formulated. • topological complexity analysis is performed using the information-theory methods. The overview of more than 280 antiperovskites as compounds based upon the units formed by condensation of XA 6 anion-centered octahedra (X = anion; A = cation) shows that there are forty-five topologically different types of antiperovskite structures, including eighteen frameworks, fourteen layers, six chains and seven finite clusters. The XA 6 octahedra may polymerize by sharing common corners, edges and faces. One A atom may be shared by no more than six XA 6 octahedra, whereas one A-A edge may be shared by no more than three octahedra. The average connectivity of an octahedron in the unit, < s >, defined as the average number of octahedra linked to a single octahedron in the complex, correlates positively with the X:A ratio. The information-based analysis of topological complexity of antiperovskite units shows that most antiperovskites are rather simple from the structural point of view with the most complex units being the layers present in the crystal structures of A 4 [N 8 O 3 A 47 ](A'N 4) 12 (A = Ca, Sr; A' = Mo, W). The information-based complexity parameters correlate with the number k' of symmetrically independent octahedra in the antiperovskite unit: the higher the value of k' , the more complex is the unit. From the chemical point of view, the review covers oxides, suboxides, oxysalts, nitrides, subnitrides, and complex halogenides. [ABSTRACT FROM AUTHOR]

The main goal of the paper is to contribute to the agenda of developing an algorithmic model for crystallization and measuring the complexity of crystals by constructing embeddings of 3D parallelohedra into a primitive cubic network (pcu net). It is proved that any parallelohedron P as well as tiling by P, except the rhombic dodecahedron, can be embedded into the 3D pcu net. It is proved that for the rhombic dodecahedron embedding into the 3D pcu net does not exist; however, embedding into the 4D pcu net exists. The question of how many ways the embedding of a parallelohedron can be constructed is answered. For each parallelohedron, the deterministic finite automaton is developed which models the growth of the crystalline structure with the same combinatorial type as the given parallelohedron. [ABSTRACT FROM AUTHOR]

Most research on polyoxometalates (POMs) has been devoted to synthetic compounds. However, recent mineralogical discoveries of POMs in mineral structures demonstrate their importance in geochemical systems. In total, 15 different types of POM nanoscale‐size clusters in minerals are described herein, which occur in 42 different mineral species. The topological diversity of POM clusters in minerals is rather restricted compared to the multitude of moieties reported for synthetic compounds, but the lists of synthetic and natural POMs do not overlap completely. The metal–oxo clusters in the crystal structures of the vanarsite‐group minerals ([As3+V4+2V5+10As5+6O51]7−), bouazzerite and whitecapsite ([M3+3Fe7(AsO4)9O8–;n(OH)n]), putnisite ([Cr3+8(OH)16(CO3)8]8−), and ewingite ([(UO2)24(CO3)30O4(OH)12(H2O)8]32−) contain metal–oxo clusters that have no close chemical or topological analogues in synthetic chemistry. The interesting feature of the POM cluster topologies in minerals is the presence of unusual coordination of metal atoms enforced by the topological restraints imposed upon the cluster geometry (the cubic coordination of Fe3+ and Ti4+ ions in arsmirandite and lehmannite, respectively, and the trigonal prismatic coordination of Fe3+ in bouazzerite and whitecapsite). Complexity analysis indicates that ewingite and morrisonite are the first and the second most structurally complex minerals known so far. The formation of nanoscale clusters can be viewed as one of the leading mechanisms of generating structural complexity in both minerals and synthetic inorganic crystalline compounds. The discovery of POM minerals is one of the specific landmarks of descriptive mineralogy and mineralogical crystallography of our time. [ABSTRACT FROM AUTHOR]

Hydrotalcite, ideally [Mg6Al2(OH)16](CO3)(H2O)4, was studied in samples from Dypingdal, Snarum, Norway (3 R and 2 H), Zelentsovskaya pit (2 H) and Praskovie–Evgenievskaya pit (2 H) (both Southern Urals, Russia), Talnakh, Siberia, Russia (3 R), Khibiny, Kola, Russia (3 R), and St. Lawrence, New York, USA (3 R and 2 H). Two polytypes, 3 R and 2 H (both 'classical'), were confirmed on the basis of single-crystal and powder X-ray diffraction data. Their chemical composition was studied by electron-microprobe analysis, infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The crystal structure of hydrotalcite-3 R was solved by direct methods in the space group R $ {\bar 3} $ m on three crystals (two data collections at 290 K and one at 120 K). The unit-cell parameters are as follows (290/290/120 K): a = 3.0728(9)/3.0626(3)/3.0617(4), c = 23.326(9)/23.313(3)/23.203(3) Å and V = 190.7(1)/189.37(4)/188.36(4) Å3. The crystal structures were refined on the basis of 304/150/101 reflections to R 1 = 0.075/0.041/0.038. Hydrotalcite-2 H crystallises in the P 63/ mmc space group; unit-cell parameters for two crystals are (data collection at 290 K and 93 K): a = 3.046(1)/3.0521(9), c = 15.447(6)/15.439(4) Å, V = 124.39(8)/124.55(8) Å3. The crystal structures were refined on the basis of 160/142 reflections to R 1 = 0.077/0.059. This paper reports the first single-crystal structure data on hydrotalcite. Hydrotalcite distribution in Nature, diagnostic features, polytypism, interlayer topology and localisation of M 2+– M 3+ cations within metal hydroxide layers are discussed. [ABSTRACT FROM AUTHOR]

Philipsburgite, Cu5Zn((As,P)O4)2(OH)6·H2O, from the Middle Pit, Gold Hill Mine, Tooele Co., Utah, USA, was studied by single-crystal X-ray diffraction and scanning electron microscopy. The empirical formula of the studied sample is (Cu4.69Zn1.23)(As0.86P0.18O4)2(OH)5.61·H2O, which agrees well with the previous reports on the mineral. Philipsburgite is monoclinic, P21/c, a = 12.385(6), b = 9.261(4), c = 10.770(5) Å, β = 97.10(1)o, V = 1225.7(9) Å3 (at 100 K), and Z = 4. The crystal structure was refined to R1 = 0.046 for 2563 unique observed reflections with |Fo| ≥ 4σF. The crystal structure of philipsburgite is isotypic to that of kipushite and can be considered as a complex three-dimensional framework consisting of two types of layers stacked parallel to the a-axis. The A-type layer is formed by the edge-sharing Jahn-Teller-distorted Cuφ6 octahedra [φ = O2−, (OH)−, H2O]. Two adjacent octahedral layers are linked via (As2O4) tetrahedra. The B-type layer is built by corner-sharing (ZnO4) and (As1O4) tetrahedra and is formed by the four- and eight-membered tetrahedral rings. The A:B ratio of the A and B layers is equal to 2:1. The hydrogen bonding network in philipsburgite is rather complex and consists of two- and three-center hydrogen bonds. The As1 site accommodates ca. 18% of P and is a preferable position for the P substitution in philipsburgite. The observed selectivity of the As1 site for P may indicate that, for the intermediate compositions with the P:As ratios close to 1:1, there is a fully ordered species with P prevalent at the As1 site and As prevalent at the As2 site. The intermediate composition would, therefore, be Cu5Zn(AsO4)(PO4)(OH)6·H2O and such a mineral can be considered as a separate species, according to the rules of the International Mineralogical Association (IMA). Philipsburgite should be considered as structurally complex with the Shannon information contents of 4.954 bits/atom and 614.320 bits/cell. The obvious reason for the structural complexity of the mineral is its modularity, i.e., the presence of two structurally distinct modules, the octahedral-tetrahedral (A) and tetrahedral (B) layers. [ABSTRACT FROM AUTHOR]

Kurchatovite and clinokurchatovite, both of ideal composition CaMgB2O5, from the type localities (Solongo, Buryatia, Russia, and Sayak-IV, Kazakhstan, respectively) have been studied using electron microprobe and single-crystal X-ray diffraction methods. The empirical formulae of the samples are Ca1.01Mg0.87Mn0.11Fe2+0.02B1.99O5 and Ca0.94Mg0.91Fe2+0.10Mn0.04B2.01O5 for kurchatovite and clinokurchatovite, respectively. The crystal structures of the two minerals are similar and based upon two-dimensional blocks arranged parallel to the c axis in kurchatovite and parallel to the a axis in clinokurchatovite. The blocks are built up from diborate B2O5 groups, and Ca2+ and Mg2+ cations in seven- and six-fold coordination, respectively. Detailed analysis of geometrical parameters of the adjacent blocks reveals that symmetrically different diborate groups have different degrees of conformation in terms of the δ angles between the planes of two BO3 triangles sharing a common O atom, featuring two discrete sets of the δ values of ca. 55° (B' blocks) and 34° (B" blocks). The stacking of the blocks in clinokurchatovite can be presented as ...(+B')(+B")(+B')(+B")... or [(+B')(+B")], whereas in kurchatovite it is more complex and corresponds to the sequence ...(+B')(+B")(+B')(-B')(-B")(-B')(+B')(+B")(+B')(-B')(-B")(-B')... or [(+B')(+B")(+B')(-B')(-B")(-B')]. The B':B" ratios for clinokurchatovite and kurchatovite are 1:1 and 2:1, respectively. According to this description, the two minerals cannot be considered as polytypes and their mutual relationship corresponds to the term modular polymorphs. From the viewpoint of information-based measures of structural complexity, clinokurchatovite (IG = 4.170 bits/atom and IG, total = 300.235 bits/cell) is structurally simpler than kurchatovite (IG = 4.755 bits/atom and IG, total = 1027.056 bits/cell). The high structural complexity of kurchatovite can be inferred from the modular character of its structure. The analysis of structural combinatorics in terms of the modular approach allows to construct the whole family of theoretically possible "kurchatovite"-type structures that bear the same structural features common for kurchatovite and clinokurchatovite. However, the crystal structures of the latter minerals are the simplest and are the only ones that have been observed in nature. The absence of other possible structures is remarkable and can be explained by either the maximum-entropy of the least-action fundamental principles. [ABSTRACT FROM AUTHOR]

The Fedorov–Groth law points out that, on average, chemical simplicity corresponds to higher symmetry, and chemically complex compounds usually have lower symmetry than chemically simple compounds. Using mineralogical data, it is demonstrated that the Fedorov–Groth law is valid and statistically meaningful, when chemical complexity is expressed as the amount of Shannon chemical information per atom and the degree of symmetry as the order of the point group of a mineral. [ABSTRACT FROM AUTHOR]

A novel polymorph of RbCuCl3 (rubidium copper trichloride), denoted ϵ‐RbCuCl3, has been prepared by chemical vapour transport (CVT) from a mixture of CuO, CuCl2, SeO2 and RbCl. The new polymorph crystallizes in the orthorhombic space group C2221. The crystal structure is based on an octahedral framework of the 4H perovskite type. The Rb+ and Cl− ions form a four‐layer closest‐packing array with an ABCB sequence. The Cu2+ cations reside in octahedral cavities with a typical [4 + 2]‐Jahn–Teller‐distorted coordination, forming four short and two long Cu—Cl bonds. ϵ‐RbCuCl3 is the most structurally complex and most dense among all currently known RbCuCl3 polymorphs, which allows us to suggest that it is a high‐pressure phase, which is unstable under ambient conditions. [ABSTRACT FROM AUTHOR]

Two quintinite polytypes, 3 R and 2 T , which are new for the Kovdor alkaline-ultrabasic complex, have been structurally characterized. The crystal structure of quintinite-2 T was solved by direct methods and refined to R 1 = 0.048 on the basis of 330 unique reflections. The structure is trigonal, P $\bar 3$ c 1, a = 5.2720(6), c = 15.113(3) Å and V = 363.76(8) Å3. The crystal structure consists of [Mg2Al(OH)6]+ brucite-type layers with an ordered distribution of Mg2+ and Al3+ cations according to the $\sqrt 3 $ × $\sqrt 3 $ superstructure with the layers stacked according to a hexagonal type. The complete layer stacking sequence can be described as ... =Ab 1 C = Cb1A =.... The crystal structure of quintinite-3 R was solved by direct methods and refined to R 1 = 0.022 on the basis of 140 unique reflections. It is trigonal, R $\bar 3$ m , a = 3.063(1), c = 22.674(9) Å and V = 184.2(1) Å3. The crystal structure is based upon double hydroxide layers [ M 2+,3+(OH)2] with disordered distribution of Mg, Al and Fe and with the layers stacked according to a rhombohedral type. The stacking sequence of layers can be expressed as ... =АB = BC = CA =... The study of morphologically different quintinite generations grown on one another detected the following natural sequence of polytype formation: 2 H → 2 T → 1 M that can be attributed to a decrease of temperature during crystallization. According to the information-based approach to structural complexity, this sequence corresponds to the increasing structural information per atom (I G): 1.522 → 1.706 → 2.440 bits, respectively. As the I G value contributes negatively to the configurational entropy of crystalline solids, the evolution of polytypic modifications during crystallization corresponds to the decreasing configurational entropy. This is in agreement with the general principle that decreasing temperature corresponds to the appearance of more complex structures. [ABSTRACT FROM AUTHOR]

Complexity is one of the important characteristics of crystal structures, which can be measured as the amount of Shannon information per atom or per unit cell. Since complexity may arise due to combination of different factors, herein we suggest a method of ladder diagrams for the analysis of contributions to structural complexity from different crystal-chemical phenomena (topological complexity, superstructures, modularity, hydration state, etc.). The group of minerals and inorganic compounds based upon the batagayite-type [M(TO4)Ï•] layers (M = Fe, Mg, Mn, Ni, Zn, Co; T = P, As; Ï• = OH, H2O) is used as an example. It is demonstrated that the method allows for the quantitative estimates of various contributions to the complexity of the whole structure. [ABSTRACT FROM AUTHOR]

Three novel copper compounds, Rb4Cu4OCl10 (I), Rb[Cu3O](SeO3)2Cl (II), and RbCu3(OH)(SeO3)Cl4(H2O)3 (III) were prepared by chemical vapor transport (CVT) reactions method from mixtures of CuO, SeO2, RbCl, and CuCl2. The crystal structures of the three compounds were determined by direct methods. Compound I is a Rb analogue of ponomarevite, K4Cu4OCl10. Its crystal structure contains {[OCu4]Cl10}4- clusters with oxocentered [OCu4]6+ tetrahedra as cores. The clusters are linked by the Rb+ cations. The crystal structure of II contains complex {[O2Cu6](SeO3)4Cl2}2- layers formed by dimers of edge-sharing [OCu4]6+ tetrahedra interlinked via selenite groups and Cl- anions. The crystal structure of III is based upon {[(OH)Cu3](SeO3)}3+ layers formed by the [(OH)Cu3]5+ tetrahedra attached to (SeO3)2- groups. The layers are linked via Cl- anions and via hydrogen bonds to H2O molecules. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) is used to determine positions of H atoms and to investigate hydrogen bonding in the crystal structures of two polymorphs of Cu3(AsO4)(OH)3: clinoclase and gilmarite. Hydrogen bonds in clinoclase involve interactions between hydroxyl groups and O atoms of arsenate tetrahedra, whereas the crystal structure of gilmarite features OH···OH bonding, which is rather uncommon in copper hydroxy-oxysalts. Information-based parameters of structural complexity for clinoclase and gilmarite show that the former is more complex (IG,total = 213.212 bits/cell) than the latter (IG,total = 53.303 bits/cell), which indirectly points out that gilmarite is metastable. This suggestion is supported by the lower density of gilmarite (4.264 g/cm3) compared to that of clinoclase (4.397 g/cm3). The hypothesis of metastable character of gilmarite is in agreement with the Goldsmith's simplexity principle and the Ostwald-Volmer rule. [ABSTRACT FROM AUTHOR]

Single crystals of four novel uranyl selenate and selenite-selenate oxysalts with protonated ethylamine molecules, (C 2 H 8 N) 2 [(UO 2 )(SeO 4 ) 2 (H 2 O)](H 2 O) ( I ), (C 2 H 8 N) 3 [(UO 2 )(SeO 4 ) 2 (HSeO 4 )] ( II ), (C 2 H 8 N)[(UO 2 )(SeO 4 )(HSeO 3 )] ( III ), and (C 2 H 8 N)(H 3 O)[(UO 2 )(SeO 4 ) 2 (H 2 O)] ( IV ) have been prepared by isothermal evaporation from aqueous solutions. Uranyl-containing 1D and 2D units have been investigated using topological approach and information-based complexity measurements that demonstrate the evolution of structural units and the increase of topological complexity with the decrease of H 2 O content. [ABSTRACT FROM AUTHOR]

The review is devoted to the start-of-the-art of the description, interpretation and classification of crystal structures in mineralogy. Among methods, the focus is on the atomic packings (including both anion and cation arrays), coordination polyhedra (both cation- and anion-centred), the concept of fundamental building blocks and related ideas, the use of networks, graphs and tilings (space partitions). The basic concepts under discussion in modern structural mineralogy include structure hierarchy (specification and compositional hierarchies are considered separately), modularity (representation of crystal structures as constructed from modules extracted from simple archetype structures) and complexity (with emphasis on static or informational and algorithmic complexities). Short historical notes are given for all of the topics considered. [ABSTRACT FROM PUBLISHER]

The tendency of high-valence xenon to form consolidated oxide structures is herein supported by the study of K4Xe3O12, the first example of a layered xenon perovskite. Xenon seems to be the only nontransition element that can adopt single-cation oxide perovskite frameworks. At the same time, peculiarities of electronic structure of xenon impose specific features on the bonding within a perovskite structure. Weak supramolecular interactions known as aerogen bonds are the linkers that maintain structural integrity of perovskite slabs in K4Xe3O12. The occurrence of aerogen bonding can provide an insight into the explosive properties of K4Xe3O12: the weakness of supramolecular interactions allows consideration of them as possible trigger bonds responsible for the detonation sensitivity of layered xenon perovskite. [ABSTRACT FROM AUTHOR]

The article discusses mineralogical crystallography and some special issues related to it, including the topic of crystallography and mineralogy, have been studied for centuries under a single discipline.

Peter Burns was extremely generous in allowing me to pursue my own research directions, simultaneously introducing me to the magic world of uranium mineralogy and crystal chemistry. First, I checked the list of the MSA awardees and medalists over the whole history of the Mineralogical Society of America and found out that I am only the second Russian citizen who was ever honored by any MSA medal. I am deeply honored and very grateful to the Mineralogical Society of America for this high recognition for three reasons. [Extracted from the article]

A new uranyl sulfate, [Co(H2O) 6]3[(UO2)5 (SO4)8 (H2O)](H2O) 5, has been synthesized using mild hydrothermal methods. The structure (monoclinic, P21 /c, a = 27.1597(14), b = 9.9858 (5), c = 22.7803 (12) Å, β = 106.520(1)°, V= 5923.2(5) ų Z = 4) has been solved by direct methods and refined on the basis of F² for all unique reflections to R1 = 0.056, calculated for the 9124 unique observed reflections (|Fo| ≥ 4σ F). It contains five symmetrically distinct uranyl pentagonal bipyra-mids and eight sulfate tetrahedra that link via the sharing of vertices between uranyl polyhedra and sulfate tetrahedra, resulting in sheets parallel to (001). Adjacent sheets are linked by hydrogen bonds to Co2+ (H2O) 6 octahedra and H2O groups located in the interlayer. The uranyl sulfate sheet contains four- and five-connected uranyl pentagonal bipyramids and three- and four-connected sulfate tetrahedra. The sheet may be constructed using modules from related structures involving pentagonal bipyramids and tetrahedra, and is readily described using a nodal representation. In general, the uranyl sulfate sheets in [Co(H2O) 6]3 [(UO2)5(SO4)8 (H2O)](H2O) 5 are more rigid than the structural units typically found in comparable uranyl molybdates, which involve the sharing of vertices between uranyl pentagonal bipyramids and molybdate tetrahedra. [ABSTRACT FROM AUTHOR]

Orange platy crystals of K2Na8 (UO2)8Mo4O24 [(S,Mo)O4, the first known uranium molybdosulfate, have been prepa-red by high-temperature solid-state reactions. The stmcture (monoclinic, C2/c, a = 24.282(4), b = 12.1170(18), c = 13.6174(17) Å, β = 106.33(1)º, V= 3845.0(9) ų Z= 4) has been solved by direct methods and refined to R1 = 0.058 on the basis of 2837 unique observed reflections. The structure consists of a three-dimensional heteropolyhedral framework based upon the [(UO2)4O4(Mo2O10)] layers parallel to (010). The layers are formed by linkage of chains of edge-sharing UO7 bipyramids running along the c axis via the Mo2O10 dimers of edge-sharing MoO6 octahedra. Linkage of the layers into a three-dimensional framework is provided by the MoO4 and SO4 tetrahedra that share comers with the MoO6 octahedra. The Na+ and K+ cations reside in framework cavities in between the uranyl molybdate layers. The stmcture of K2Na8 (UO2)8Mo4O24 [(S,Mo)O4] is yet another complex derivative of the U2MoO8 structure type. [ABSTRACT FROM AUTHOR]

A new mineral beshtauite, (NH4)2(UO2)(SO4)2⋅2H2O, was found in the oxidation zone of the Beshtau uranium deposit, Mount Beshtau, Stavropol region, Northern Caucasus, Russia, and named after the locality. It is associated with rozenite, gypsum, lermontovite, and older marcasite, pyrite, halloysite, and opal. Beshtauite occurs as well-shaped short-prismatic crystals up to 0.1 x 0.15 x 0.2 mm, their clusters and crusts up to 0.5 mm across growing on marcasite. Beshtauite is transparent, light green. The luster is vitreous. The mineral fluoresces strongly yellow-green under both short- and long-wave UV irradiation. It is brittle. The Mohs hardness is ca. 2. Cleavage was not observed. Dcalc is 3.046 g/cm³. Beshtauite is optically biaxial (+), α = 1.566(3), β = 1.566(3), γ = 1.592(3), 2Vmeas < 10°. The chemical composition (wt%, electron microprobe data, H2O by difference) is: (NH4)2O 10.33, UO3 53.21, SO3 29.40, H2Ocalc 7.06, total 100.00. Content of (NH4)2O was calculated from measured nitrogen content: 5.56 wt% N. The empirical formula, calculated on the basis of 12 O apfu, is (NH4)2.12U0.99S1.96O9.91 (H2O) 2.09. Beshtauite is monoclinic, P21/c, a = 7.7360(8), b = 7.3712(5), c = 20.856(2) Å, β = 102.123(8)°, V = 1162.76(19) Å3, Z = 4 (from single-crystal X-ray diffraction data). The strongest reflections of the X-ray powder pattern [d (Å), I(hkl)] are: 6.86, 100(011, 102); 5.997, 19(012); 5.558, 15(102); 5.307, 36(111,110); 5.005, 35(013,112); 3.410, 38(114,204,106); 3.081, 24(016); 2.881, 20(106,123). The crystal structure was solved by direct methods and refined on the basis of 2677 independent reflections with I > 4σ(I) to R1 = 0.093. The structure is based upon [UO2(SO4)2(H2O)]2- layers consisting of corner-sharing UO6 (H2O) pentagonal bipyramids and SO4 tetrahedra. The layers are coplanar to (102) and are linked via hydrogen bonding that involve interlayer NH4+ ions and H2O molecules. Beshtauite is important indicator mineral: its presence can be considered as an evidence of transportation of U6+ in nature in forms of mobile complexes of uranyl cation with ammonia or polyamines. [ABSTRACT FROM AUTHOR]

Compounds with the fresnoite structure type possess remarkable chemical diversity and a range of unique physical properties, including nonlinear optical (NLO) activity. K2Sb(P2O7)F, which was reported recently, belongs to this group and its structure is not novel in terms of either the topology or local coordination geometry around the Sb3+ cations. The crystallographic disorder observed in the fresnoite‐type structures can be explained by twinning, which is frequent for non‐centrosymmetric crystals. It is argued by Krivovichev and Bindi that the previously reported K2Sb(P2O7)F has a fresnoite structure type that is not novel in terms of either the topology or local coordination geometry around the Sb3+ ions. They argue that the crystallographic disorder observed in fresnoite‐type structures can be explained by twinning, which is frequent for non‐centrosymmetric crystals. [ABSTRACT FROM AUTHOR]

Compounds with the fresnoite structure type possess remarkable chemical diversity and a range of unique physical properties, including nonlinear optical (NLO) activity. K2Sb(P2O7)F, which was reported recently, belongs to this group and its structure is not novel in terms of either the topology or local coordination geometry around the Sb3+ cations. The crystallographic disorder observed in the fresnoite‐type structures can be explained by twinning, which is frequent for non‐centrosymmetric crystals. [ABSTRACT FROM AUTHOR]

The discovery of the diffraction of X-rays on crystals opened up a new era in our understanding of nature, leading to a multitude of striking discoveries about the structures and functions of matter on the atomic and molecular scales. Over the last hundred years, about 150 000 of inorganic crystal structures have been elucidated and visualized. The advent of new technologies, such as area detectors and synchrotron radiation, led to the solution of structures of unprecedented complexity. However, the very notion of structural complexity of crystals still lacks an unambiguous quantitative definition. In this Minireview we use information theory to characterize complexity of inorganic structures in terms of their information content. [ABSTRACT FROM AUTHOR]

Die Entdeckung, dass Röntgenstrahlen an Kristallen gebeugt werden, markierte den Beginn einer neuen wissenschaftlichen Ära, die eine Vielzahl von erstaunlichen Entdeckungen über die Strukturen und Funktionen von Materie auf atomarer und molekularer Skala hervorgebracht hat. Über die letzten hundert Jahre wurden ungefähr 150 000 anorganische Kristallstrukturen aufgeklärt und bildlich dargestellt. Das Aufkommen neuer Technologien wie Flächendetektoren und Synchrotronstrahlung führte zur Strukturlösung von kristallinen Verbindungen nie dagewesener Komplexität. Allerdings fehlt bis heute eine klare quantitative Definition der strukturellen Komplexität von Kristallen. In diesem Kurzaufsatz nutzen wir die mathematische Informationstheorie, um den Komplexitätsgrad anorganischer Strukturen in Form ihres Informationsgehaltes zu charakterisieren. Ursache und Komplexität: Anorganische Kristallstrukturen können mithilfe von informationsbasierten Komplexitätsmaßen analysiert werden. Es zeigt sich, dass strukturelle Komplexität durch die Anordnung von nanoskaligen Bausteinen, durch Modularität und durch die Bildung von Übergittern als Ergebnis lokaler atomarer Ausordnung oder displaziver Phasenumwandlungen erzeugt wird. [ABSTRACT FROM AUTHOR]

The article reviews studies conducted on the description and evaluation of structures of inorganic compounds with main emphasis on anion-centered tetrahedral. It presents the systematic description of several anion-centered tetrahedral including OCu4, OPb4 and OBi4. It mentions that the properties of inorganic compounds depend upon the electronic properties of the metal atoms present in the center.

Abstract: Shannon information theory is applied to the quantitative evaluation of topological and structural complexity of zeolite frameworks. Within this approach, content of the reduced unit cell volume is considered as a message with atoms as symbols. Two atoms are considered equivalent, if they belong to the same crystallographic orbit. The framework complexity is characterized by its total topological information content, IG , total . Topological complexity parameters are calculated for the 201 zeolite structure types listed in the International Zeolite Association Zeolite Structure Database. On the basis of the proposed complexity measures, zeolite frameworks can be classified into very simple, simple, intermediate, complex, and very complex. The six most complex zeolite frameworks are [IG , total in bits]: SFV [19557.629], ITV [2825.097], IMF [2614.111], CLO [2413.449], and LTN [2285.985]. The six simplest zeolite frameworks are: SOD [16.529], BCT [19.020], ABW [23.020], NPO [28.529], EDI and NAB [32.603]. The sodalite–cancrinite group of zeolite frameworks is used to investigate evolution of complexity within modular series of structurally related zeolites. The topological complexity measures can be used to investigate evolution of complexity during crystallization and transformation of zeolites. [Copyright &y& Elsevier]

Abstract: Single crystals of the new compounds Li6[(UO2)12(PO4)8(P4O13)] (1), Li5[(UO2)13(AsO4)9(As2O7)] (2), Li[(UO2)4(AsO4)3] (3) and Li3[(UO2)7(AsO4)5O)] (4) have been prepared using high-temperature solid state reactions. The crystal structures have been solved by direct methods: 1—monoclinic, C2/m, a=26.963(3)Å, b=7.063(1)Å, c=19.639(1)Å, β=126.890(4)°, V=2991.2(6)Å3, Z=2, R 1=0.0357 for 3248 unique reflections with |F 0|≥4σF ; 2—triclinic, , a=7.1410(8)Å, b=13.959(1)Å, c=31.925(1)Å, α=82.850(2)°, β=88.691(2)°, γ=79.774(3)°, V=3107.4(4)Å3, Z=2, R 1=0.0722 for 9161 unique reflections with |F 0|≥4σF ; 3—tetragonal, I 41/amd, a=7.160(3)Å, c=33.775(9)Å, V=1732(1)Å3, Z=4, R 1=0.0356 for 318 unique reflections with |F 0|≥4σF ; 4—tetragonal, , a=7.2160(5)Å, c=14.6540(7)Å, V=763.04(8)Å3, Z=1, R 1=0.0423 for 1600 unique reflections with |F 0|≥4σF . Structures of all the phases under consideration are based on complex 3D frameworks consisting of different types of uranium polyhedra (UO6 and UO7) and different types of tetrahedral T O4 anions ( T =P or As): PO4 and P4O13 in 1, AsO4 and As2O7 in 2, and single AsO4 tetrahedra in 3 and 4. In the structures of 1 and 2, UO7 pentagonal bipyramids share edges to form (UO5)∞ chains extended along the b axis in 1 and along the a axis in 2. The chains are linked via single T O4 tetrahedra into tubular units with external diameters of 11Å in 1 and 11.5Å in 2, and internal diameters of 4.1Å in 1 and 4.5Å in 2. The channels accommodate Li+ cations. The tubular units are linked into 3D frameworks by intertubular complexes. Structures of 3 and 4 are based on 3D frameworks composed on layers united by (UO5)∞ infinite chains. Cation–cation interactions are observed in 2, 3, and 4. In 2, the structure contains a trimeric unit with composition [OU(1)O]–U(13)–[OU(2)O]. In the structures of 3 and 4, T-shaped dimers are observed. In all the structures, Li+ cations are located in different types of cages and channels and compensate negative charges of anionic 3D frameworks. [Copyright &y& Elsevier]

Abstract: The three new framework Rb uranyl phosphates and arsenates with anionic parts based on different type of polymeric anions have been prepared by high-temperature solid-state reactions: Rb4[(UO2)6(P2O7)4(H2O)] (1), Rb2[(UO2)3(P2O7)(P4O12)] (2), Rb[(UO2)2(As3O10)] (3). The crystal structures of the synthesized compounds have been solved by direct methods: 1—monoclinic P21/c, a=9.672(1)Å, b=12.951(1)Å, c=32.231(3)Å, β=90.116(4)°, V=4037.3(6)Å3, Z=4, R 1=0.0926 for 6351 unique reflections with ; 2—monoclinic, P21/c, a=6.791(1)Å, b=16.155(3)Å, c=19.856(4)Å, β=97.48(5)°, V=2159.8(7)Å3, Z=4, R 1=0.0286 for 3617 unique reflections with ; 3—orthorhombic, Pbcn, a=10.558(1)Å, b=11.037(1)Å, c=11.464(1)Å, V=1335.9(2)Å3, Z=4, R 1=0.0489 for 1384 unique reflections with . The structures of title are compounds based on 3D negatively charged frameworks with chemical compositions [(UO2)6(P2O7)4(H2O)]4− in 1, [(UO2)3(P2O7)(P4O12)]2− in 2 and [(UO2)2(As3O10)]− in 3. These negative charges are compensated by rubidium cations which are in the channels of 1 and closed cages in structures of 2 and 3. The channels in 1 are directed along the a direction and have minimum dimensions ∼5Å×6Å. This is the first example of porosity generation through solid state synthesis in uranyl compounds. For the first time in uranium chemistry polymeric anionic groups P4O12 and As3O10 were observed in structure of 2 and 3. [Copyright &y& Elsevier]

Abstract: Four new Li uranyl phosphates and arsenates have been prepared by high-temperature solid-state reactions: α-Li[(UO2)(PO4)] (1), α-Li[(UO2)(AsO4)] (2), β-Li[(UO2)(AsO4)] (3) and Li2[(UO2)3(P2O7)2] (4). The structures of the compounds have been solved by direct methods: 1—triclinic, , a=5.0271(1)Å, b=9.8799(2)Å, c=10.8920(2)Å, α=108.282(9)°, β=102.993(8)°, γ=104.13(1)°, V=470.69(2)Å3, Z=4, R 1=0.0415 for 2786 unique reflections with |F 0|⩾4σF ; 2—triclinic, , a=5.129(2)Å, b=10.105(3)Å, c=11.080(3)Å, α=107.70(2)°, β=102.53(3)°, γ=104.74(3)°, V=501.4(3)Å3, Z=4, R 1=0.055 for 1431 unique reflections with |F 0|⩾4σ F; 3—triclinic, , a=5.051(1)Å, b=5.303(1)Å, c=10.101(1)Å, α=90.31(1)°, β=97.49(1)°, γ=105.08(1)°, V=258.80(8)Å3, Z=2, R 1=0.0339 for 2055 unique reflections with |F 0|⩾4σ F; 4—triclinic, , a=5.312(1)Å, b=6.696(1)Å, c=12.542(1)Å, α=94.532(9)°, β=99.059(8)°, γ=110.189(7)°, V=409.17(10)Å3, Z=2, R 1=0.0565 for 1355 unique reflections with |F 0|⩾4σ F. The structures of all four compounds are based upon 3-D frameworks of U and T polyhedra (T=P, As). Phases 1 and 2 are isostructural and consist of U2O12 dimers and UO6 square bipyramids linked by single TO4 tetrahedra. The structure of 3 consists of 3-D framework of corner-sharing UO6 bipyramids and AsO4 tetrahedra. In the structure of 4, the framework is composed of U2O12 dimers, UO6 bipyramids and P2O7 dimers. In all the compounds, Li+ cations reside in framework cavities. The topologies of the 3-D frameworks can be described as derivatives of the PtS (cooperite) network. [Copyright &y& Elsevier]

Abstract: A brief overview of nanostructured inorganic actinide compounds, i.e., compounds with nanoscale clusters and structural units, is given. Only structures that are accessible via X-ray diffraction analysis are considered (i.e., highly ordered assemblies of molecular units with at least one dimension of more than 1nm). Zero-dimensional (0D) actinide based nanostructures are represented by a new family of self-assembling actinide nanospheres recently reported by Burns et al. [P.C. Burns, K.-A. Hughes Kubatko, G. Sigmon, B.J. Fryer, J.E. Gagnon, M.R. Antonio, L. Soderholm, Angew. Chem. Int. Ed. 44 (2005) 2135]. The nanospheres are comprised of linear actinyl-peroxide building blocks, and their persistence as stable entities in alkaline solutions has been confirmed. Krivovichev et al. [S.V. Krivovichev, V. Kahlenberg, R. Kaindl, E. Mersdorf, I.G. Tananaev, B.F. Myasoedov, Angew. Chem. Int. Ed. 44 (2005) 1134; J. Am. Chem. Soc. 127 (2005) 1072] have recently reported synthesis and structures of two uranium(VI) compounds, K5[(UO2)3(SeO4)5](NO3)(H2O)3.5 (1) and (C4H12N)14 [(UO2)10(SeO4)17(H2O)] (2), containing nanometer-sized tubules formed by corner sharing of U6+O7 pentagonal bipyramids and SeO4 tetrahedra. Actinide peroxide nanospheres and uranyl selenate nanotubules represent the first examples of nanoscale structures in inorganic actinide compounds. These findings demonstrate the possibility of nanoscale fabrication for actinides in higher oxidation states, and a whole new range of uranium-based nanotubular and nanocomposite materials can be expected. [Copyright &y& Elsevier]

Abstract: Single crystals of [C10H26N2][(UO2)(SeO4)2(H2O)](H2SeO4)0.85(H2O)2 (1), [C10H26N2][(UO2)(SeO4)2] (H2SeO4)0.50(H2O) (2), and [C8H20N]2[(UO2)(SeO4)2(H2O)] (H2O) (3) were prepared by evaporation from aqueous solution of uranyl nitrate, selenic acid and the respective amines. The structures of the compounds have been solved by direct methods and structural models have been obtained. The structures of the compounds 1, 2, and 3 contain U and Se atoms in pentagonal bipyramidal and tetrahedral coordinations, respectively. The UO7 and SeO4 polyhedra polymerize by sharing common O atoms to form chains (compound 1) or sheets (compounds 2 and 3). In the structure of 1, the layers consisting of hydrogen-bonded [UO2(SeO4)2(H2O)]2− chains are separated by mixed organic–inorganic layers comprising from [NH3(CH2)10NH3]2+ molecules, H2O molecules, and disordered electroneutral (H2SeO4) groups. The structure of 2 has a similar architecture but a purely inorganic layer is represented by a fully connected [UO2(SeO4)2]2− sheet. The structure of 3 does not contain disordered (H2SeO4) groups but is based upon alternating [UO2(SeO4)2(H2O)]2− sheets and 1.5-nm-thick organic blocks consisting of positively charged protonated octylamine molecules, [NH3(CH2)7CH3]+. The structures may be considered as composed of anionic inorganic sheets (2D blocks) and cationic organic blocks self-organized according to competing hydrophilic–hydrophobic interactions. Analysis of the structures allows us to conclude that the charge-density matching principle is observed in uranyl compounds. In order to satisfy some basic peculiarities of uranyl (in general, actinyl) chemistry, it requires specific additional mechanisms: (a) in long-chain-amine-templated compounds, protonated amine molecules interdigitate; (b) in long-chain-diamine-templated compounds, incorporation of acid–water interlayers into an organic substructure is necessary; (c) the inclination angle of the amine chains may vary in order to modify surface area of an organic substructure. [Copyright &y& Elsevier]

Abstract: Three new uranyl tungstates, A 8[(UO2)4(WO4)4(WO5)2] (A=Rb (1), Cs (2)), and Rb6[(UO2)2O(WO4)4] (3), were prepared by high-temperature solid-state reactions and their structures were solved by direct methods on twinned crystals, refined to , 0.042, and 0.052 for 1, 2, and 3, respectively. Compounds 1 and 2 are isostructural, monoclinic P21/n, (1): , , , , , and (2): , , , , , . There are four symmetrically independent U6+ sites that form linear uranyl [O=U=O]2+ cations with rather distorted coordination in their equatorial planes. There are six W positions: W(1) and W(2) have square-pyramidal coordination (WO5), whereas W(3), W(4), W(5), and W(6) are tetrahedrally coordinated. The structures are based upon a novel type of one-dimensional (1D) [(UO2)4(WO4)4(WO5)2]4− chains, consisting of WU4O25 pentamers linked by WO4 tetrahedra and WO5 square pyramids. The chains run parallel to the a-axis and are arranged in modulated pseudo-2D-layers parallel to (010). The A+ cations are in the interlayer space between adjacent pseudo-layers and provide a 3D integrity of the structures. Compounds 1 and 2 are the first uranyl tungstates with 2/3 of W atoms in tetrahedral coordination. Such a high concentration of low-coordinated W6+ cations is probably responsible for the 1D character of the uranyl tungstate units. The compound 3 is triclinic, P1¯, , , , , , , . There are four U positions in the structure with a typical coordination of a pentagonal bipyramid that contain uranyl ions, UO2 2+, as apical axes. Among eight W sites, the W(1), W(2), W(3), W(4), W(5), and W(6) atoms are tetrahedrally coordinated, whereas the W(7) and W(8) cations have distorted fivefold coordination. The structure contains chains of composition [(UO2)2O(WO4)4]6− composed of UO7 pentagonal bipyramids and W polyhedra. The chains involve dimers of UO7 pentagonal bipyramids that share common O atoms. The dimers are linked into chains by sharing corners with WO4 tetrahedra. The chains are parallel to [−101] and are arranged in layers that are parallel to (111). The Rb+ cations provide linkage of the chains into a 3D structure. The compound 1 has many structural and chemical similarities to its molybdate analog, Rb6[(UO2)2O(MoO4)4]. However, the compounds are not isostructural. Due to the tendency of the W6+ cations to have higher-than-fourfold coordination, part of the W sites adopt distorted fivefold coordination, whereas all Mo atoms in the Mo compound are tetrahedrally coordinated. Distribution of the WO5 configurations along the chain extension does not conform to its ‘typical’ periodicity. As a result, both the chain identity period and the unit-cell volume are doubled in comparison to the Mo analog, which leads to a new structure type. [Copyright &y& Elsevier]

Abstract: Crystals of two new inorganic compounds, M2[(UO2)3(SeO4)5](H2O)16 (M=Co, Zn), have been prepared by evaporation from aqueous solutions. The structures of the compounds have been determined and refined using single crystal diffraction data. The Co compound is triclinic, space group P , a =10.458(2), b =11.032(2), c =17.893(4)Å, α =89.451(17), β =90.280(17), γ =61.761(14)°, V =1818.5(6)Å3, R 1 =0.075 for 6611 independent observed reflections. The Zn phase is triclinic as well, space group P , a =10.438(3), b =11.063(4), c =17.895(6)Å, α =89.19(3), β =89.85(3), γ =61.72(2)°, V =1819.5(10)Å3, R 1 =0.081 for 4134 independent observed reflections. Both compounds are isostructural. Their structures are based upon sheets with the chemical composition [(UO2)3(SeO4)5]4−. The sheets are parallel to (001) and are formed by corner sharing between UO7 pentagonal bipyramids and SeO4 2− tetrahedra. The [M2+(H2O)6]2+ octahedra (M=Co, Zn) and additional H2O molecules are located between the sheets providing linkage via hydrogen bonding. Topology of the uranyl selenate sheets in the structures of M2[(UO2)3(SeO4)5](H2O)16 (M=Co, Zn) is discussed and its relation to the known topologies of uranyl compounds are considered on the basis of a nodal representation. [Copyright &y& Elsevier]

Abstract: Single crystals of a new compound, Zn2[(UO2)3(SeO4)5](H2O)17, were prepared by evaporation from aqueous solution. The crystal structure (orthorhombic, Pbca, a = 18.4288(10), b = 19.9793(11), c = 20.6901(9)Å, V = 7618.0(7)Å3, Z = 8) has been solved by direct methods and refined to R1 = 0.047 on the basis of 7805 independent observed reflections. The structure is based upon [(UO2)3(SeO4)5]4- sheets consisting of corner-sharing UO7 pentagonal bipyramids and SeO4 groups. The sheets are oriented parallel to the (010) plane and are strongly modulated with the modulation vector oriented approximately parallel to the [101] direction. The Zn(H2O)6 octahedra and additional H2O groups are located in the interlayer providing three-dimensional linkage of the sheets via hydrogen bonds. Zn2[(UO2)3(SeO4)5](H2O)17 is isostructural to previously reported Mg2[(UO2)3(CrO4)5](H2O)17 and Cu2[(UO2)3((S,Cr)O4)5](H2O)17. [Copyright &y& Elsevier]

Abstract: Two new chiral open-framework uranyl molybdates, (UO2)0.82[C8H20N]0.36[(UO2)6(MoO4)7(H2O)2](H2O)n (1) and [C6H14N2][(UO2)6(MoO4)7(H2O)2](H2O)m (2) have been synthesized by hydrothermal methods. The structures of 1 and 2 have been refined using X-ray diffraction data collected at −127°C. The structure of 1 [orthorhombic, C2221, a=12.2303(15), b=18.966(2), c=22.392(3) Å, V=5194.0(11) Å3] has been refined to R1=0.043 on the basis of 4126 unique observed reflections. The structure of 2 [orthorhombic, C2221, a=11.3256(15), b=19.860(3), c=23.731(3) Å, V=5337.8(12) Å3] has been refined to R1=0.056 on the basis of 3519 unique observed reflections. The structures of 1 and 2 are based upon complex chiral [(UO2)6(MoO4)7(H2O)2] frameworks of corner-sharing UO7 bipyramids and MoO4 tetrahedra. In addition to framework U sites, the structure of 1 contains an additional, partially-occupied and disordered U(4) site, located within the framework cavities and coordinated by several disordered anions to form the complex [(UO2)(H2O)5]2+ cation. The structure of 2 contains disordered DABCO (1,4-diazabicyclo[2.2.2]-octane) molecules. The geometrical parameters of the uranyl molybdate frameworks in the structures of 1 and 2 are significantly different. The a parameter of 1 is about 0.9Å longer than that of 2, whereas the b and c parameters of 1 are shorter than those of 2 (∼0.9 and 1.3Å, respectively). This occurs due to the adaptation of the [(UO2)6(MoO4)7(H2O)2]2− framework to the shape of the complex [(UO2)(H2O)5]2+ cation in 1. Analysis of the U–O–Mo bond angles of the frameworks indicates the U–O(15)–Mo and U–O(20)–Mo links are the most flexible. The transition from 2 to 1 involves an increase of the U–O(15)–Mo and U–O(20)–Mo angles from 146.7° to 169.0° and from 151° to 171°, respectively. [Copyright &y& Elsevier]

Abstract: A new chiral 6:7 open-framework uranyl molybdate, [C6H16N]2[(UO2)6(MoO4)7(H2O)2](H2O)2, has been synthesized by hydrothermal methods. The structure has been refined using single-crystal X-ray diffraction data collected at 20 and −127°C. The 20°C structure [orthorhombic, C2221, a=11.3045(14), b=19.962(6), c=24.416(5)Å, V=5510(2)Å3] has been refined to R1=0.046 on the basis of 6093 unique observed reflections. The −127°C structure [orthorhombic, P212121, a=11.211(4), b=19.880(10), c=24.421(8)Å, V=5443(4)Å3] has been refined to R1=0.047 on the basis of 6951 unique observed reflections. The structures are based upon topologically identical frameworks of corner-sharing UO7 pentagonal bipyramids and MoO4 tetrahedra. The extra-framework H2O groups and protonated triethylamine molecules reside in the framework cavities. In the C2221 structure at 20°C, H2O and [C6H16N]+ molecules filling the chiral channels along [001] are disordered, whereas, in the P212121 structure at −127°C, they are perfectly ordered. The symmetry difference between structures at 20°C and −127°C is the result of a C2221→P212121 second order phase transition that involves ordering of extra-framework protonated amine molecules and H2O groups, and distortion of the flexible [(UO2)6(MoO4)7(H2O)2]2− uranyl molybdate framework. On the basis of measurements of intensities of reflections that violate absence conditions of C-centering cell, the temperature of the phase transition is estimated as −11°C. [Copyright &y& Elsevier]

Abstract: Crystals of a new framework uranyl molybdate, [(C2H5)2NH2]2[(UO2)4(MoO4)5(H2O)](H2O), were synthesized from a solution of UO2(CH3COO)2·2H2O, MoO3, diethylamine and HCl in H2O at 220°C. The structure was studied at −127°C. The compound is hexagonal, space group P6522, a=11.3612(13), c=52.698(8)Å, V=5890.7(13)Å3, Z=3. The structure has been refined to R1=0.050 (wR2=0.100; S=0.985) on the basis of 3103 unique observed reflections. The structure consists of a three-dimensional framework of composition [(UO2)4(MoO4)5(H2O)]2− that consists of UO7 pentagonal bipyramids that share equatorial corners with MoO4 tetrahedra. The framework contains a three-dimensional system of channels. The first system of channels is parallel to [001] and has the dimensions 7.0×7.0Å, which result in a crystallographic free diameter (effective pore width) of 4.3×4.3Å (based on an oxygen radius of 1.35Å). Other channels run parallel to [100], [110] and [010] and have dimensions 5.2×7.1Å (giving an effective pore width of 2.5×4.4Å). One symmetrically unique [(C2H5)2NH2]+ cation and H2O molecule reside in the framework cavities. The channels parallel to [001] are chiral and are centered about a 65 screw axis. The uranyl framework with U:Mo=4:5 in the structure of [(C2H5)2NH2]2[(UO2)4(MoO4)5(H2O)](H2O) represents the third known type of chiral uranyl molybdate framework. Its relationships to the frameworks with U:Mo=5:7 and 6:7 can be understood in terms of fundamental chains that have related but yet different topological structure. [Copyright &y& Elsevier]

The structure of shafranovskite, ideally K2Na3(Mn,Fe,Na)4[Si9(O,OH)27](OH)2⋅nH2 O (n ∼ 2.33), a K-Na-manganese hydrous silicate from Kola peninsula, Russia, was studied using synchrotron X-ray radiation and a MAR345 image-plate detector at the Swiss-Norwegian beamline of the European Synchrotron Radiation Facility (ESRE Grenoble, France). The structure [trigonal, space group P31c, a = 14.519(3), c = 21.062(6) Å, V = 3844.9(14) ų] was solved by direct methods and partially refined to R1 = 0.085 (wR2 = 0.238) on the basis of 2243 unique observed reflections (¦Fo¦ ≥ 4σF). Shafranovskite is a 2:1 hydrous phyllosilicate. Sheets of Mn and Na octahedra (O sheets) are sandwiched between two silicate tetrahedral sheets (T1 and T2). The 2:1 layers are parallel to (001). The upper tetrahedral sheet T1 consists of isolated [Si13(O,OH)37] islands composed of three six-membered rings. The octahedral sheet O consists of Mnφ6, Na1φ6, and Na2φ6 octahedra (φ = O, OH, H2O). This unit can be considered as a trioctahedral sheet with each 20th octahedron vacant. The lower tetrahedral sheet T2 consists of [Si13(O,OH)37] islands linked into a sheet through an additional SiO3OH tetrahedron. The Na3, K1, K2 atoms, and H2O32 groups are between the 2:1 layers and provide their linkage along c. [ABSTRACT FROM AUTHOR]

The average crystal structures of two natural porous titanosilicates of the labuntsovite group, lemmleinite-Ba and lemmleinite-K, ideally Na4K4Ba2Ti8 (Si4O12)4O4(OH)4⋅8H2O and Na4K4K2Ti8(Si4 O12)4O2(OH)6⋅8H2O, respectively, have been refined from single crystal X-ray diffraction data. Both samples represent an extensive solid solution with labuntsovite sensu strictu Na4K4D2Ti8(Si4O12)4O4(O H)4⋅10H2O where D = Mn, Fe, and Mg. In addition to the sharp Bragg reflections both crystals, space group C2/m, a = 14.3, b = 13.8, c = 7.75 Å, β = 117°, exhibit diffuse layers at c*/2 intervals indicating faulty superstructures with c = 15.7 Å. The diffuse layers consist of two types of reflections. The dominant type is strongly diffuse and smeared along a* indicating an I-centered Bravais lattice. The other type is very sharp but also weak and is in agreement with a C-centered lattice. Models for both superstructures have been developed on the basis of crystal-chemical principles and their theoretical diffraction patterns have been calculated and compared with the observed diffuse layers yielding excellent qualitative agreement. X-ray structure refinements of the average structure at -160 and 22 °C indicate temperature independent (static) disorder of Ti within rather rigid TiO6 octahedra connected to chains that extend along a. This Ti disorder is interpreted in terms of long-range order of OH and O in the superstructures where these anions occupy the corner-connecting octahedral apices in an ordered fashion. An additional effect of OH, O order is an ordered arrangement of... [ABSTRACT FROM AUTHOR]

The crystal structure of yuksporite, (Sr, Ba)2K4 (Ca,Na)14 (〉,Mn,Fe) {(Ti,Nb)4(O,OH)4[Si6O17]2[Si2O7] 3}(H2O,OH)n, where n ∼ 3 [monoclinic, P21/m, a = 7.126(3), b = 24.913(6), c = 17.075(7) Å, β = 101.89(3)°, V = 2966.4(17) Å3] has been solved using X-ray synchrotron radiation data collected from a needle-like crystal with dimensions of 6 x 6 x 50 μm3 at the Swiss-Norwegian beamline BM01 of the European Synchrotron Research Facility (ESRF, Grenoble, France). The structure was refined to R1 = 0.101 on the basis of 2359 unique observed reflections with ¦Fo¦ ≥ 4σF. The structure of yuksporite is based upon titanosilicate nanorods elongated along a and with an elliptical cross-section of ca. 16 x 19 Å = 1.6 x 1.9 nm. Silicate tetrahedra form double xonotlite-like chains 1∞ [Si6O17] oriented parallel to (001). Two 1∞ [Si6O17] chains are linked into a rod via TiO6 octahedra and Si2O7 double tetrahedra. The {(Ti,Nb)4(O,OH)4[Si6O17]2[Si2O7] 3} nanorods are porous. The internal pores are defined by eight-membered rings (SMR) with open diameters of 3.2 Å. The interior of the titanosilicate nanorods is occupied by Sr, Ba, K, and Na cations and H2O molecules. The nanorods are separated by walls of Ca coordination polyhedra that are parallel to (010) and link the rods into a three-dimensional structure. [ABSTRACT FROM AUTHOR]

A method of graphical representation of heteropolyhedral units is applied to a wide range of salts of inorganic oxoacids (phosphates, arsenates, sulfates, chromates, molybdates, selenates, selenites, tellurites, etc.). Only those heteropolyhedral units that fulfill the following criteria are considered: (i) units with corner-sharing between coordination polyhedra only; (ii) units with no linkage between chemically and geometrically identical polyhedra; (iii) only zero- (finite clusters), one- (chains) and two- (sheets) dimensional units. More than 80 different topologies are considered. For 2D units (sheets), the concepts of basic graph and topological isomerism are formulated. Three different types of geometrical isomerism are recognized for chains, sheets and finite clusters: orientational isomerism, cis-trans -isomerism, and isomerism induced by the presence of cations with stereoactive lone pairs of electrons. Different geometrical isomers can be described by means of orientation matrices and connectivity diagrams. Relationships between different topologies are investigated. [ABSTRACT FROM AUTHOR]

The crystal structure of glagolevite, Na(Mg,Al)6[Si3AlO10](OH,O)8, a new mineral from the Kovdor alkaline massif, Kola peninsula, Russia, has been solved and refined to R1 = 0.117, calculated from 1503 unique observed reflections (Fo ≥ 4σFo), and to R1 = 0.118 for all 1550 unique reflections. The specimen contained several polytypes; the crystal studied yielded triclinic space group C1, a = 5.3580(11), b = 9.2810(19), c = 14.574(3) Å, α = 90.00(3), β = 97.08(3), ϒ= 90.00(3)°, V= 719.2(3) ų. Glagolevite is the first mineral of the chlorite group that contains Na atoms located between the 2:1 layers and the interlayer octahedral sheets. The Na atoms are in sevenfold coordination. The Na(O,OH)7 polyhedron is a trigonal prism with one of the triangular bases extended to a square. The tetrahedral sheets show disorder owing to polytype intergrowths. Tetrahedral site occupancies correlate with the occupancies of the Na sites. The polytypic composition of the crystal studied is estimated at 57% IIb-6, 31% IIb-2, and 12% IIb-4. [ABSTRACT FROM AUTHOR]

Cellular automata are used as dynamic topological models of crystal structures based upon frameworks consisting of fundamental building blocks. Structure is considered as an automaton that works in accord with a prescribed program. Cellular automata models are constructed for metal sulfide frameworks in minerals and compounds of the pentlandite–djerfisherite–bartonite series, for zeolite ACO and compounds with pharmacosiderite structure, leucophosphite, phosphovanadylite etc. [ABSTRACT FROM AUTHOR]